What a real star map actually calculates
- Star positions from a measured catalog (not a stock illustration).
- The planets — Jupiter, Saturn, Venus, Mars — only where they truly were that night.
- The Moon in its real phase, with the correct tilt.
- Corrections for how the sky shifts: precession, nutation, aberration, refraction.
Five signs a star map is just decoration
- It never asks for the time of day — only the date.
- The preview looks identical no matter what date you type.
- There is no Moon, or the Moon is always full.
- It cannot do dates far in the past or future.
- It never mentions how the positions are calculated.
Does the time of day matter?
Yes — a lot. The whole sky rotates through the night, and the Moon moves about half a degree every hour. Two maps of the same day at different hours are genuinely different. A service that ignores the time is drawing decoration, not your sky.
How StarMap does it
StarMap uses the same models professional astronomy uses: VSOP87 for the planets, ELP2000/82 for the Moon, and the AT-HYG catalog (865,000 stars measured by the ESA Hipparcos and Gaia missions).
It applies nine astronomical corrections, works for any place on Earth and any date between 1600 and 2200, and publishes every model and source it uses so anyone can verify it. You also see a free preview before paying.